One useful type of buck boost switching regulator is shown in U.S. Pat. No. 4,395,675. Such a regulator utilizes two synchronized switches, often called a ground switch and a battery switch. Those switches operate at either the same or different duty cycles, in response to a freely variable, regulator, feedback signal, to control energy storage in a two terminal inductor element and energy delivery from that element to the regulator output. However, such regulators are difficult to control if operated so that the duty cycles for the ground switch and the battery switch approach too close to the 0% point and the 100% point, respectively. Illustrative difficulties may include, for example, discontinuities in the regulator output voltage.
Another buck boost regulator is shown in a U.S. Pat. No. 4,245,286 to J. Paulkovich et al., and employs current and temperature limiting functions to inhibit operation of a pulse width modulator and thus terminate switching transistor drives in the regulator.